Hand propelled devices provide not only a means of mobility and independence for people who have difficulty walking, but can also provide a means of efficient travel and a form of exercise for able bodied people. In addition, Hand propelled devices can provide an alternative means for children to commute short distances and to play with their peers. The main drawback to hand/arm propelled devices in the industry is that hand propelled devices are inefficient and require substantial hand and arm strength and stamina to operate for long durations. As such, the majority of exercise devices and children's toys operate through foot and leg propulsion.
In situations where individuals have difficulty walking, hand/arm propelled devices, such as wheelchairs, are a practical method of human powered travel. The usual means of propelling wheelchairs is through the use of annular hand rails attached to the two main driving wheels. This method is not efficient and contorts the rider's body in a potentially unhealthy manner. The continual unidirectional movement and hunched over riding position may be unhealthy as it tends to constrict the chest and arms. Additionally, the use of annular hand rails to propel the wheels is an inefficient use of energy, and can be exhausting to use over longer distances and on rough terrain. Other attempts at designing alternative mechanisms for wheelchair propulsion suffer similar problems, as they feature a power stroke in one direction only, which is strenuous on the upper body.
Additionally, most hand propelled devices, such as wheelchairs, are difficult to steer. The mechanism of steering generally involves altering the speed of one wheel independent of the other wheel. Other mechanisms involve the use of a steering mechanism that alters the direction of the front wheel(s) of the propelled device, but requires removal of at least one hand from the drive wheel.
Inventions such as U.S. Pat. No. 8,186,699 (Green), U.S. Pat. No. 5,007,655 (Hanna), US Patent Publication US2013/0015632 (Winter), and U.S. Pat. No. 6,158,757A (Tidcomb) have been devised in order to provide hand propelled wheeled vehicles.
Green discloses a manual propulsion mechanism for wheelchairs. The mechanism utilizes a lever pivotally mounted to the hub of each drive wheel such that the wheelchair operator can propel the chair with push/pull movements of the lever. Forward and reverse propulsion is accomplished by a system of two one-way, opposing clutches contained within wheel hubs that are controlled by shifting of the lever handgrips. Only one of the strokes of the lever is converted into rotary motion of the wheel at any given time. The return stroke is only engaged when the reverse direction is selected by the operator through movement of the hand grip, which as a result propels the wheelchair backwards. Green is an inefficient use of the lever system as it uses only one of the stroke directions to propel the wheelchair forward, and can only feasibly rotate the wheel less than one quarter of a full rotation (360°) for one stroke.
Hanna discloses a lever propelled wheelchair wherein only the forward stroke propels the wheels as the return stroke does not affect the rotation of the wheel as the clutch disconnects the lever from the wheel drivetrain. Hanna employs a rack that connects the lever to the wheel drivetrain. The rack converts the linear motion of the lever into rotational force of the drivetrain by linearly running over the drivetrain gear, causing the gear and the wheel, to rotate. Hanna, like Green is a less efficient system, as only one of the two strokes is employed to propel the wheelchair forward. Additionally, the unidirectional effort can cause physiological strain.
Winter discloses a manually powered wheelchair propelled through the use of a left and right lever. The drivetrain is comprised of driven and driving sprockets which convert the linear motion to rotational motion. The diametric ratio between the driven and driving sprocket is either 4:1 or 3:1 and gives mechanical advantage. Hand position along the tall levers can be modified to change the amount of torque applied. As with Green and Hanna, Winter only uses the forward stroke to propel the wheels, the return stroke ratchets and resets the gear train for the next power stroke. This style of ratcheting lever only allows a fraction of a full rotation (360°).
Tidcomb discloses an operator-propelled vehicle driven by a hand lever system, where a flexible cable member is connected to the drive lever, and wrapped around a wheel drum. The state of tension on the wrapped cable is selected by the operator by closing a grip lever to assume a tensioned state driving the chair, or releasing the grip lever assuming a slackened state allowing for freewheeling. As such, when the lever is moved through a push or pull stroke, and depending on the grip lever position, the wheel will rotate with the movement of the lever under a tensioned cable, and the wheel will not be acted on by a slackened cable. The operator can only use one stroke direction to propel the wheel forward, and the mechanism necessitates learning a coordinated technique to tension and slacken the cables at the appropriate times during power and return strokes to effectively use the vehicle at speed.
Other inventions have attempted to harness forward and backward linear strokes to provide rotary motion. U.S. Pat. No. 4,282,442 (Massinger) discloses a device for converting linear reciprocal motion to continuous rotary motion whereby both forward and backward strokes of the reciprocal motion contribute to the power output of the device. Massinger employs two one-way clutches, wherein during the forward stroke, the first clutch engages and the second clutch slips, while during the backward stroke, the first clutch slips and the second clutch engages. Massinger discloses a complicated system with numerous gears and a large number of moving parts, intended for use in industries such as power generation and heavy machinery. The design is not specifically tailored to vehicle locomotion.
As such, there is a need in the industry for a hand propelled wheeled device that is efficient at converting the linear force applied by the operator into rotational force at the main wheels. The efficiency stems from converting both the forward and return strokes to forward rotation of the wheels, thus propelling the wheeled device forward. In addition, a single stroke of the lever should equate to a full rotation of the mechanism, thus, the operator is not expending energy with multiple strokes for just one wheel rotation. None of the prior art provides for a full wheel rotation with just one power stroke. Furthermore, the steering mechanism of the prior art is inefficient, if present at all. With traditional wheelchair steering mechanisms, the operator steers by manipulating the speed of the main wheels and not through a dedicated steering mechanism, as the operator's hands are occupied with propulsion of the chair. This is an inefficient method of steering, as the operator uses friction to slow down one wheel in order to turn in one direction.
None of the prior art provides for a mechanism of steering the wheeled vehicle outside varying the speed of the rear wheels, except Tidcomb. Although a steering mechanism is present in Tidcomb's design, the steering wheels are not controlled to follow the proper arc for a given turning radius. The steering wheels are fixed to both rotate at the same angle relative to a straight forward path leading to frictional losses and wheel slippage, which could negatively impact running speed turning performance.
Further, the propulsion mechanism disclosed herein can be adapted to perform tasks other than that of propelling the hand powered wheeled vehicle. It can be used in any case where the need arises for a mechanism requiring reciprocal, linear input to be converted into unidirectional rotational output, such as pumps, electricity generators, or any other applicable industrial scenario.